Citizen scientists and university students monitor noise pollution in cities and protected areas with smartphones

Lucy Zipf; Richard B. Primack; Matthew Rothendler

doi:10.1371/journal.pone.0236785

Peer Review History

Original SubmissionSeptember 3, 2019
4 Dec 2019 Decision Letter - Andreas Mueller, Editor PONE-D-19-23835 Citizen scientists and university students monitor noise pollution in cities and protected areas with smartphones PLOS ONE Dear Ms. Zipf, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. ============================== Please apologize for the delay, due to the late arrival of one of the reviwer reports. The reviews are very positive and constructive throughout. I decided to follow the "major revision" recommendation of the 2nd reviewer, for the reasons given in her/his report, However, I also think that the points put forward by the reviewers are quite easy to deal with, and strongly encourage you to resubmit the paper with the necessary changes. 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Occasions like this can help raise the citizens' awareness of noise and provide them with a scientific method to collect and interpret measurement data themselves. I recommend publishing this article when the following points of criticism can be addressed satisfactorily. Please see the attachment Reviewer #2: **************************************************************************************** see attached file **************************************************************************************** ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. 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Attachments Attachment Submitted filename: Review on PONE-D-19-23835.pdf Attachment Submitted filename: PONE-D-19-23835 review_an.pdf https://doi.org/10.1371/journal.pone.0236785.r001
Revision 1
22 Apr 2020 Author Response Major Suggestions from Reviewers 1 & 2: 1. Lacking data and information in the “Materials & Methods” section There is no information about technical data of the measurements you report, such as sensitivity, accuracy, precision, spatial and temporal resolution Thanks for this suggestion. We did originally provide a reference for other studies that used the app, SPLnFFT, but we have now provided more technical information, additional reference, and performed our own assessment. See below. Please add these data, or at least estimates for them. • Most importantly: a) add a comparison measurement with a professional noise measurement equipment. As the data collection with your participant groups has already taken place, a measurement carried out by yourself would be sufficient. Great point, we added a comparison between our iPhone method and a type 2 sound meter, as well as included more direct references to papers that have assessed the SPLnFFT app. b) add a comparison to a theoretical prediction for the decrease of road noise with distance (based on known result for a line/1D source) We have decided to omit this figure as we did not feel it added to the message of the paper, and instead focus on the method and the resulting noise maps. c) Additionally, a discussion of the quality of data obtained in the “Discussion” section would be most useful for you readers. Through the paper we have included additional information on the quality of noise measurements with the iPhone and the specific methods of our study. • The suitability to use smartphones in acoustics, also for measuring noise, has already been studied in depth in the physics education literature. It has been shown that they are reliable tools for educational purposes. Since sound measurement with smartphones is one key aspect to enable the CS project in this paper, this should not remain unmentioned. Good point, we have followed this suggestion and we now discuss these technical points throughout the paper and we cite appropriate literature about the technical capabilities of smartphone noise measurements. We mention this in the methods, and we reference some acoustics examples in the introduction. 2. It should be better worked out where the added value lies in the recording of one's own measurement data as a citizen. • The keyword could be authentic data and ownership of data (see, for example, Tara O'Neill and Angela Calabrese Barton: Uncovering Student Ownership in Science Learning: The Making of a Student Created Mini-Documentary or Enhag and Niedderer: Two dimensions of student ownership of learning during small-group work in physics and the references therein). Thank you for these additional references; we have drawn from O’Neill as well as other authors to more clearly convey the benefits to the citizen scientists and our intent to connect volunteers to their local environment though the collection of and ownership over real world data with conservation applications. We have included more information in the intro and discussion about the projects benefits for citizen scientists and their ownership of data collection in a local conservation area. References to papers in the education and citizen science literature have also been added. • A main characteristic of citizen science is that citizens learn to collect and interpret data independently. But in this study you control the data recording very strictly by specifying special calibration rules and even intervene people by telephone if you are skeptical about their measurement data. How is this compatible with the goal of making citizens as autonomous as possible and not degrading them to data producers? We provide training to the citizen scientists so that they are capable of collecting and interpreting data on their own. Teaching them how to calibrate their phones is important so that their measurements are more precise. The skills that we provide are transferable. Volunteers can monitor noise pollution themselves in their own environment in a way that fulfills their own needs and concerns. Additionally, we very rarely had to intervene to correct a data collection mistake – however we see the ability to correct any errors mid-monitoring as an advantage of the method. It is better than allowing a volunteer to spend many hours submitting incorrect and unusable data. Reviewer 1 1. line 10: Noise distributions are also often simulated simply on the basis of theoretical models. This statement could be added. Thank you for the suggestion, this has been added. 2. line 14: in in Thanks! Fixed in line 13 3. line 21 citizen science (2x) Thanks! Fixed in keywords 4. line 46: Smartphones have also often been used in physics education (research) for learning in acoustics, e.g., see Hirth, Michael, Jochen Kuhn, and Andreas Müller. "Measurement of sound velocity made easy using harmonic resonant frequencies with everyday mobile technology." The Physics Teacher 53.2 (2015): 120-121. And Klein, P., Hirth, M., Gröber, S., Kuhn, J. & Müller, A. (2014). Classical experiments revisited: smartphones and tablet PCs as experimental tools in acoustics and optics. Physics Education, 49(4), 412. In particular, it was emphasized that the accuracy of measurement for educational purposes is sufficient. Thank you, we have added these references (line 49-51) and a statement about their success for education in lines 49-51 5. line 49: please provide literature about using smartphones in the context of air pollution, I am not aware about that Lim CC, Kim H, Vilcassim MJR, Thurston GD, Gordon T, Chen LC, et al. Mapping urban air quality using mobile sampling with low-cost sensors and machine learning in Seoul, South Korea. Environ Int. 2019; doi:10.1016/j.envint.2019.105022 Good point! The above reference has been added. 6. line 57: create This has been changed to produce in line 61 7. line 66: so-called bioblitz Thanks! Added line 71 8. line 77: Please point out that the character of the single-day events what adds the new value Added information about the value of single day events in lines 68-81 9. line 80-81: It reads as if the combination of data sources would take place in this article. Please attenuate the statement. Statement amended! 10. Introduction in general: Please give more attention to the work of Shim et al 2016, which was published in the same journal. They took measurements over the period of one week, including working with Android devices. Please briefly present this work here. We have described the work of Shim et al and others more clearly in the introduction including describing their methods and the differences between our approaches (84-91). We have also commented on the models of phones used in ours and other noise studies in the methods (151-160) 11. Line 91: Here you write about a several-hour time period, elsewhere about a single-day event. Please stay consistent. Thanks, added single-day event has now been used consistently through the ms. 12. Line 95-104: The mentioned buildings and areas could be highlighted in the pictures, possibly by a label. Good point, we changed the labeling in the figures so the areas mentioned in text are now labeled on the maps. 13. Line 125-125: I have a few questions about the method: Why was the in-app calibration not used? Thanks - this is now addressed in line 180-190. The in-app calibration requires a quiet space which is not always available in the field. How much do the results of an in-app calibration vary compared to a calibration with a standard instrument? In the materials and methods, we added a comparison between our iPhone method and a type 2 sound meter, as well as included more direct references to papers that have assessed the SPLnFFT app. We found the app and iPhone to consistently overestimate noise values by about 2.8 dB in comparison with the type 2 sound meter, which closely corresponds with what others have found. Besides this overestimate, we found the app and iPhone to be very precise across multiple measurements at various decibel levels. In text lines 162-178 Is it still possible to speak of citizen science if such a control is necessary? It is standard practice in science to calibrate recording devices before taking measurements. That way, we can increase the accuracy of measurements. In practice, the iPhones were typically within 1 or 2 decibels of each other before calibration, which is minor in comparison to the 40 or so decibels of variation in sound across sites. Does the calibration remain constant over the measuring period, i.e. over 90-120 minutes? Based on our experience, the calibration remains constant over the 2-3 hour period of people taking measurements. The accuracy does not change over such short time periods. As a test we took 10 measurements at 40-60dB and found the average difference between iPhone and type 2 noise meter at time 0 was +2.6dB; when we repeated the same measurements two hours later, the average difference was +2.3dB, which is very consistent. What can you say about the measuring range of the app, especially for noises smaller than 30dB? MEMS microphones typically capture measurements as low as 30 dB and as high as 120-130 dB, which is sufficient for our method and typical of type 2 sound level meters (in text line 152-153). Our lowest reading was 32 dB in the field, so the lack of sensitivity of these meters to sound levels below 30 should not impact the study. Why did the citizens have to send the data after each measurement and why not send the complete data set at the end of the route? This is addressed in lines (232-242). The main reason is that the app does not readily store the data. Also, this method allowed us to track noise levels and the progress of volunteers in real time. 14. Line 125: what is the common standard? This is now more explicitly stated in 180-190. The common standard is a researcher iPhone that we calibrated the volunteer iPhones to. 15. Line 134: Which criteria were used to select the routes and the density of the measuring points along the routes? This has been added in lines 207-213. The routes were selected along streets, paths, and trails, and the point density was selected to cover the largest amount of area during the single-day events. 16. Line 160-162: That sounds like a lot of effort. Please comment on the purpose of citizen science. On the one hand you want to have very accurate measurement data and monitor it pretty closely, on the other hand citizens should have the responsibility for the measurement. How does that fit together? The value of including citizen scientists despite the technical challenges of this approach is now addressed throughout the ms, as well as above under the major concerns. 17. Line 197: Wind can have a huge influence, as I know from my own measurements. Has it been checked that people have stood with their backs to the wind? Should a windscreen be used for the microphones in the future? We have added information on tests we ran to determine the effect of shielding the phone with one’s body, and information on the addition of windscreens for the phone in lines 215-119. We found that when there was a modest and steady breeze, there was no detectable effect of using the body as a wind screen; that is, wind did not affect the measurements. Screening the iPhone with one’s body was effective when there was a strong and gusting wind. Using a windscreen and microphone with each iPhone might increase accuracy slightly in windy conditions, but would have added to the expenses and logistical challenges of the volunteers. We provide more detail about this in the paper. 18. Line 218: What does local regression mean? What is local about it? What equation was used to the data and what is the message from the regression? We are removing this figure as it does not add to our overall findings and is not discussed in the text. 19. Line 238: Maybe I'm too pedantic there but detailed is a matter of definition. For a particle physicist, the amount of data you created is very small. Maybe you find a different description. We now address this issue more directly, and specify that including volunteers yields maps with about 3 times more data than would be possible with the research group alone during the time available. See lines 317-320. 20. Line 244: what exactly is our method. Please explain and summarize it briefly in the discussion We have now included a brief description in place of the word method in line 317. 21. Line 255: Wouldn't it have been possible to ask the participants afterwards if they had used the smartphone again? The project took place about 2 years ago.... This is a good point, we emailed the volunteers (1/6/20) to see if they had used the app / monitored noise since the event, but received a low response rate (3 total respondents); many of the participants are students and professionals who may have just been returning after the holidays. Therefore we cannot comment on the use of the app following the events. Of three respondents one had used the app to check the noise level within their apartment. 22. Line 263: You write that volunteers can monitor noise pollution independently. Doesn't that contradict the high level of control you have tried to achieve? This discrepancy is more clearly addressed in lines 344-353, as well as above under the major concerns. 23. Line 294: Are there suitable apps for Android users that you can recommend and that have appeared in the meantime? The primary problem with taking measurements across devices is the microphone differences, not the app itself. We chose to use iPhones because 42% of the smartphones owned in the US are iPhones and all iPhones have standard microphones. Android microphones vary across phone types and manufacturers and are therefore much more variable. There are high quality Android monitoring apps, but the microphone variation would likely be too great for this application. We included more information about the limits and advantages of iPhone in 162-178. Fig. 3 A: Why did you decide to make this division in the legend? It would be nice to be able to identify the areas mentioned in the text in the maps. Good point! We changed the maps in Figure 3 to identify the areas in text rather than circle areas on the maps. 24. Additional References: Please also consider this work: Zappatore, Marco, Antonella Longo, and Mario A. Bochicchio. "Crowd-sensing our smart cities: A platform for noise monitoring and acoustic urban planning." (2017): 53-67. Thanks! This study has been referenced throughout the intro as we reference past smartphone based noise monitoring programs. Reviewer 2 1. As you highlight two kinds of participant groups in the title, you should compare them (eg. by a chi2 test) in terms of measurement quality, e.g. % removed (table 1) or other data you might have; for the former it looks as if there is no difference between citizen science participants and college students (of a health science track), and this is interesting for the community. Great point, we have included a chi2 calculation to compare removed observations between groups. 2. table 1: doesn’t fit on the page Thanks! We have reformatted table 1. 3. research for and refer to other lit. beyond noise monitoring in the spirit of your approach. eg: a) earthquakes Kong, Q., Allen, R. M., Schreier, L., & Kwon, Y. W. (2016). MyShake: A smartphone seismic network for earthquake early warning and beyond. Science advances, 2(2), e1501055. b) radioactivity Laquai, B. Open Geiger citizen science project; Available online: www.opengeiger.de Bottollier-Depois, J.F.; Allain, E.; Baumont, G.; Berthelot, N.; Clairand, I.; Couvez, C.; Darley, G.; Henry, B.; Jolivet, T.; Laroche, P.; et al. OPEN RADIATION: A collaborative project for radioactivity measurement in the environment by the public. EPJ Web Conf. 2017, 153, 08002. [CrossRef] Keller, O., Benoit, M., Müller, A., & Schmeling, S. (2019). Smartphone and Tablet-Based Sensing of Environmental Radioactivity: Mobile Low-Cost Measurements for Monitoring, Citizen Science, and Educational Purposes. Sensors, 19(19), 4264 Beser, A.M. How Citizen Science Changed the Way Fukushima Radiation is Reported. National Geographic Society Newsroom, 13 February 2016. Thanks! We have added some of these interesting papers and made more reference to the existing literature on citizen science phone-based monitoring programs in 44-54. Attachments Attachment Submitted filename: Noise_response to reviewers_17Jan20.docx https://doi.org/10.1371/journal.pone.0236785.r002
26 Jun 2020 Decision Letter - Andreas Mueller, Editor PONE-D-19-23835R1 Citizen scientists and university students monitor noise pollution in cities and protected areas with smartphones PLOS ONE Dear Dr. Zipf, Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Aug 10 2020 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file. Please include the following items when submitting your revised manuscript: A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'. A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'. An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'. If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter. If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols We look forward to receiving your revised manuscript. Kind regards, Andreas Mueller Academic Editor PLOS ONE [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation. Reviewer #1: All comments have been addressed Reviewer #2: All comments have been addressed ******** 2. Is the manuscript technically sound, and do the data support the conclusions? The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented. Reviewer #1: Yes Reviewer #2: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: N/A Reviewer #2: Yes ****** 4. Have the authors made all data underlying the findings in their manuscript fully available? The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified. Reviewer #1: Yes Reviewer #2: Yes ****** 5. Is the manuscript presented in an intelligible fashion and written in standard English? PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here. Reviewer #1: Yes Reviewer #2: Yes ****** 6. Review Comments to the Author Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters) Reviewer #1: The authors did a good job in addressing all issues that I pointed out during the first revision. The paper has improved a lot and I favour publication. Reviewer #2: all points were addressed, but please correct the following minor issue. The spatial resolution values in table 1 are given with senseless precision (up to 5 digits and 2 decimals, while you know the area in km2 probably at best with an error of a few %). Please use a reasonable precision throughout the paper. ****** 7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy. Reviewer #1: Yes:** Pascal Klein Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0236785.r003
Revision 2
1 Jul 2020 Author Response Major Suggestions from Reviewers: 1. The spatial resolution values in table 1 are given with senseless precision (up to 5 digits and 2 decimals, while you know the area in km2 probably at best with an error of a few %). Please use a reasonable precision throughout the paper. Thanks for this suggestion. We fixed the issue and now report the values in whole numbers, which is much more appropriate precision. Attachments Attachment Submitted filename: Noise_response to reviewers_1July20.docx https://doi.org/10.1371/journal.pone.0236785.r004
15 Jul 2020 Decision Letter - Andreas Mueller, Editor Citizen scientists and university students monitor noise pollution in cities and protected areas with smartphones PONE-D-19-23835R2 Dear Dr. Zipf, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Andreas Mueller Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0236785.r005
Formally Accepted
4 Aug 2020 Acceptance Letter - Andreas Mueller, Editor PONE-D-19-23835R2 Citizen scientists and university students monitor noise pollution in cities and protected areas with smartphones Dear Dr. Zipf: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Andreas Mueller Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0236785.r006

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